Propeller



Apfil 24, 19 28.

J. s. BANKRAT PROPELLER Filed Feb. 10. 1927 JOHN 151 BA NK/PAT INVENTOR ATTORNEY gflw ' my propeller.

Patented Apr. 24', 1928.

, PATENT OFFICE.

JOHN S. BANKRAT, OF HEMPSTEAD, NEW YORK.

PROPELLEB.

Application filed February 10, 1927. Serial No. 167,233.,

My invention relates to airplane or boat propellers and has a particular reference to propellers provided with internal passages for the fluid in which the propeller operates.

In ordinary propellers there is always a certain amount of vacuum formed at the rear portion of the propeller blades which vacuum interferes with the forward movement of the propeller and reduces its efli-1 ciency. In order to obviate this difiiculty I provide my propeller with a hollow hub and internal passages through ,which the fluid is admitted under pressure inside'of the blades from which it emerges through suitably located holes located at points where vacuum usually forms.

My invention is more fully described in the accompanying specification and drawing in which- Fig. 1 is a sectionalelevation of my prop eller (showing portions only of the blades),

.ig. 2 is a top view of same, tional elevation taken endwise, and Fig. 4 is a diagrammatic view illustrating action of My propeller comprises a hub 1 mounted on a motor shaft 2 and fastened with a nut 3 (or in any other suitable manner.) The front portion of the hub is made hollow being provided. with a circular cavity 4. Blades 5 are attached to the hub. These blades are made hollow inside with cavities 6 in communication with the cavity 4. A plurality of small holes 7 are provided in the rear portion of the blades at points where the undesirable vacuum is likely to be formed (Fig. 4).

The hub has reinforcing straight webs 8 between the blades and, spiral guiding webs 9 directing the air to the inner port-ions of the blades as shown with arrows '10.

The total area of the holes 7 issmaller than the cross-sectional area of the hub cavity, so that the air in the blade cavities willbe under a certain amount of pressure.

This is necessary in order to provide a sulficient velocity to the fluid emerging from the holes 7.

Fig. peller.

4 illustrates the action of my pro- The blade 5 (shown in section) moves in direction of an arrow 11 under action of the motor (the movement ofrotation), the movement of translation bemg indicated with an arrow 12. An undesirable Fig. 3 is a secvacuum 13 is formed at the rear of the blade, tending to retard the forward movement of the propeller. ever, with streams 14 of the'fluid under pressure. This fluid in case of an airplane is air and for boats'water.

The formation of this vacuum depends to a large extent on. the velocity of the movement of translation, and. with my arrangement this velocity also increases the fluid pressure in the blades and, consequently, the yelo'city of the fluid streams 14. This action is entirely automatic, more fluid being admitted to the rear of the blades when more vacuum is formed.

It is possible,

blades by means of a suitable apparatus, such as a blower, pump or engine exhaust.

VV-ith ordinary propellers it is necessary to provide the hub with a sharp pointed cap in order to reduce the air (or water) resistance. With my propeller this is not neccssary, as the whole front portion of the hub which contains the cavity, practically does not offer any resistance to the translatory movement, the fluid passing freely inside.

I claim as In invention:

In a propel er, the combination with a cylindricalhub, of means tomount said hub on a shaft, an outer cylinder concentric with of course, to assist this action by introducing additional fluid in the This vacuum is filled, howsaid hub and attached to said 'hub in the rating said clearance for said blades, and

spiral guiding surfaces in said partitions extending from the front end of said hub to .the inside of said hollow blades and forming smooth passages for air from the front of forming a circular clearance in front a said hub to the inside of said blades, said blades being provided with a plurality of small apertures in a communication with the inside of said blades and extending through the full length of said blades on one side. i

Signed at Hempstead, in the county of Nassau and State of New York this seventh day of February A. D. 1927 JOHN s. simian.

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